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"""SelectionWidget classes.
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Represents an enumeration using a widget.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (c) 2013, the IPython Development Team.
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#
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# Distributed under the terms of the Modified BSD License.
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#
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# The full license is in the file COPYING.txt, distributed with this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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from collections import OrderedDict
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from threading import Lock
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from .widget import DOMWidget
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from IPython.utils.traitlets import Unicode, List, Bool, Any, Dict, TraitError
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from IPython.utils.py3compat import unicode_type
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#-----------------------------------------------------------------------------
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# SelectionWidget
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#-----------------------------------------------------------------------------
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class _SelectionWidget(DOMWidget):
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"""Base class for Selection widgets
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``values`` can be specified as a list or dict. If given as a list,
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it will be transformed to a dict of the form ``{str(value):value}``.
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"""
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value = Any(help="Selected value")
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values = Dict(help="""Dictionary of {name: value} the user can select.
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The keys of this dictionary are the strings that will be displayed in the UI,
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representing the actual Python choices.
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The keys of this dictionary are also available as value_names.
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""")
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value_name = Unicode(help="The name of the selected value", sync=True)
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value_names = List(Unicode, help="""Read-only list of names for each value.
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If values is specified as a list, this is the string representation of each element.
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Otherwise, it is the keys of the values dictionary.
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These strings are used to display the choices in the front-end.""", sync=True)
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disabled = Bool(False, help="Enable or disable user changes", sync=True)
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description = Unicode(help="Description of the value this widget represents", sync=True)
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def __init__(self, *args, **kwargs):
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self.value_lock = Lock()
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self._in_values_changed = False
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if 'values' in kwargs:
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values = kwargs['values']
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# convert list values to an dict of {str(v):v}
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if isinstance(values, list):
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# preserve list order with an OrderedDict
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kwargs['values'] = OrderedDict((unicode_type(v), v) for v in values)
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DOMWidget.__init__(self, *args, **kwargs)
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def _values_changed(self, name, old, new):
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"""Handles when the values dict has been changed.
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Setting values implies setting value names from the keys of the dict.
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"""
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self._in_values_changed = True
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try:
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self.value_names = list(new.keys())
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finally:
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self._in_values_changed = False
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# ensure that the chosen value is one of the choices
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if self.value not in new.values():
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self.value = next(iter(new.values()))
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def _value_names_changed(self, name, old, new):
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if not self._in_values_changed:
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raise TraitError("value_names is a read-only proxy to values.keys(). Use the values dict instead.")
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def _value_changed(self, name, old, new):
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"""Called when value has been changed"""
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if self.value_lock.acquire(False):
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try:
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# Reverse dictionary lookup for the value name
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for k,v in self.values.items():
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if new == v:
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# set the selected value name
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self.value_name = k
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return
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# undo the change, and raise KeyError
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self.value = old
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raise KeyError(new)
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finally:
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self.value_lock.release()
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def _value_name_changed(self, name, old, new):
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"""Called when the value name has been changed (typically by the frontend)."""
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if self.value_lock.acquire(False):
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try:
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self.value = self.values[new]
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finally:
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self.value_lock.release()
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class ToggleButtonsWidget(_SelectionWidget):
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_view_name = Unicode('ToggleButtonsView', sync=True)
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class DropdownWidget(_SelectionWidget):
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_view_name = Unicode('DropdownView', sync=True)
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class RadioButtonsWidget(_SelectionWidget):
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_view_name = Unicode('RadioButtonsView', sync=True)
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class SelectWidget(_SelectionWidget):
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_view_name = Unicode('SelectView', sync=True)
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